The Types of Plant Growth Regulators on Grain Yield and Yield Components of Barley (Hordeum vulgare L.) in Water Stress Condition Mohammad Reza Askarnejad1, Ali Soleymani1,2*, and Hamid Reza Javanmard1 1-Department of Agronomy and Plant Breeding, Isfahan (Khorasgan) Branch, Islamic Azad University, Isfahan, Iran 2-Plant Improvement and Seed Production Research Center, Isfahan (Khorasgan) Branch, Islamic Azad University, Isfahan, Iran *Corresponding email address: a.soleymani444@gmail.com Received: 20 March 2022 Accepted: 2 June 2022 Abstract Iran is climatically located in semi-arid and arid zones, as stressful environment in the world, Barley is one of the stress-tolerant crops that adapted to salinity and drought simultaneously. In order to evaluate the impacts of different plant growth regulators (PGR) on the grain yield and yield components of irrigated barley crop under water low or deficit irrigation condition, an experiment was conducted as a split plot with three replications in two different experimental fields, namely Abarkuh and Faragheh in 2018-2019 cropping year. Main plots were irrigation after the evaporation from the class A pan, namely control (80 mm) (S1), 100 mm (S2), and 120 mm (S3), and the subplots were the PGR application by spraying water (control) (P1), gibberellic acid (GA3 at 110 mg/l) (P2), salicylic acid (SA at 1.5 mM) (P3), benzyl adenine (BA6 at 60 mg/l) (P4), GA3 (110 mg/l) + SA (1.5 mM) (P5), and superoxide dismutase (SOD at 5 mg/l) (P6) solutions in water. In this experiment the effects of experiment treatments were affected plant height, leaf area index (LAI), the number of tillers per plant, peduncle length, spike length, the number of seed per spike, one thousand grain weight, grain yield, biological yield, harvest index (HI), and grain protein significantly. The highest values of plant height (102.64 cm), leaf area index (3.62), the number of tillers per plant (4.27), peduncle length (26.02 cm), spike length (7.87 cm), the number of seed per spike (33.09), one thousand grain weight (39.86 g), grain yield (3.06 t/ha), biological yield (5.62 t/ha), harvest index (54.53%), and grain protein (11.82%) was related to 80 mm evaporation from the Pan class A and combined application GA3 and SA. All PGRs, particularly the combined application of SA and GA3 followed by superoxide dismutase significantly increased nutrient uptake, grain yield, grain protein, and yield components of barley. In conclusion, it is important to use tested PGR to increase barley yield and yield components particularly under drought stress condition. پرونده مقاله